The present invention relates to a reaction detecting device which changes a temperature of a reaction specimen such as deoxyribonucleic acid (DNA) sampled from blood, a test body or the like to promote reaction such as incubation (amplification) and which detects a reaction situation, that is, an amplification amount by incubation.
Heretofore, an incubator is used in amplification of a reaction specimen such as DNA sampled from blood, a test body or the like. This incubator includes an automatic synthesis unit of DNA or RNA by a phosphotriesterification process. The incubator is constituted by covering an outer periphery of a reactor with a thermal block, this thermal block being provided with a thermo module having a heating and cooling function due to the Peltier effect, the thermo module being buried.
In general, a method of synthesizing DNA or the like by the phosphotriesterification process is a method in which four steps of masking, deprotection, drying and condensation are repeated in this order to thereby promote proliferation of DNA. For this purpose, in the synthesis unit, a specimen obtained by mixing DNA and various types of reagents or solutions is placed in the reactor. Electric conduction of the thermo module is controlled by a thermistor to heat the thermal block at +42° C., thereby performing the three steps of masking, drying and condensation. Moreover, a conducting direction of the thermo module is changed to cool the thermal block at +20° C., thereby performing the deprotection step (see Japanese Utility Model Application Laid-Open No. 62-44979).
Moreover, such a DNA synthesis step is executed a plurality of times to thereby amplify DNA up to a predetermined amount. To measure the amplification amount of this reaction specimen, heretofore, at the end of the synthesis, a reaction container is taken out of the incubator, and the amplification amount of DNA, that is, concentration of a reaction liquid is measured using a separately installed reaction detecting device.
The reaction detecting device for use in this case generally measures the amplification amount of a reactant by an optical measurement process. Examples of such a reaction detecting device include devices described in, for example, Japanese Patent Application Laid-Open Nos. 10-201464 and 2003-329590. Here, a basic principle of reaction detecting will be described with reference to a basic conceptual explanatory view of FIG. 12. It is to be noted that a reaction liquid which is a liquid reaction specimen is prepared by a fluorescent dyestuff selected so as to meet excitation requirements of a reaction specimen component which is regarded as a detection object or which is known, and emission or radiation characteristics of the component.
Moreover, this reaction liquid is contained in a reaction container 100 having its top opened. Here, a plurality of reaction containers 100 for use, that is, 96 reaction containers in this case are connected to one another on a plane, and a plurality of reaction specimens can be measured once. The top opening of each reaction container 100 is openably closed by a lid member 101 such as a light transmitting film or cap, and the reaction liquid contained in the container is inhibited from being evaporated. It is to be noted that in FIG. 12, each reaction container 100 is shown in a vertically sectional side view.
It is to be noted that each reaction container 100 containing this reaction liquid is contained in a reaction block 102 formed of a thermally conductive material such as aluminum. In this reaction block 102, there are formed a plurality of holding holes for holding the respective reaction containers 100, 96 holding holes in the present embodiment, so that the respective reaction containers 100 are held. The temperature of this reaction block 102 is controlled to heat or cool the block, thereby incubating (amplifying) the reaction specimen. It is to be noted that the reaction containers 100 contained in the reaction block 102 are pressed in the reaction block 102 by a press member 103 having a good thermal conductivity.
Moreover, a reflective plate 104 constituted of a flat plate is disposed above the reaction containers 100. This reflective plate 104 reflects, toward the reaction containers 100, light from, for example, a light source lamp 105 which emits the light in a direction parallel to the reaction containers 100. In an optical path positioned between this light source lamp 105 and the reflective plate 104, a band pass filter 106 is disposed which transmits only light having a wavelength required for exciting fluorescence among components of the light emitted from the light source lamp 105. Accordingly, from the light emitted from the light source lamp 105, via the band pass filter 106, the only light having the wavelength required for the reaction specimen to excite the fluorescence is obtained via the band pass filter 106, and thereafter the reaction liquid of the reaction container 100 is irradiated.
Thereafter, the reaction liquid in the reaction containers 100 emits the fluorescence in accordance with the concentration of the reaction specimen in the reaction liquid owing to a function of the fluorescent dyestuff. The fluorescence and the reflected light pass through a band pass filter 107 disposed above the reaction containers 100 to irradiate a camera 108 constituting reaction detecting means disposed above the filter. It is to be noted that this band pass filter 107 transmits only the fluorescent component, and the camera 108 is irradiated with the fluorescence only. In FIG. 12, since the reflective plate 104 is constituted of a material which transmits the fluorescence, the fluorescence emitted from the reaction specimen of each reaction container 100 passes through the reflective plate 104 to irradiate the camera 108.
Moreover, when the fluorescence photographed by the camera 108 constituting the reaction detecting means is measured, the reaction specimen can be analyzed, that is, a type or a concentration (amplification amount) of the reaction specimen can be detected.
However, in the reaction detecting device described in the above second document, a plurality of reaction containers contained in the reaction block are provided with the device which optically detects the amplification reaction, but in such a constitution, to once detect the amplification reactions of all the reaction containers, the light from the light source is guided into the reaction containers by use of an optical fiber line. Therefore, there is a problem that costs of components constituting the device increase. Therefore, to avoid the increase of the cost due to the optical fiber line, it is necessary to guide the light from the light source into the reaction specimen in each reaction container at low cost. To receive the fluorescence from the reaction liquid with high sensitivity, it is necessary to guide the light from the light source from above the reaction container, and receive the reflected light including the fluorescence from the light source by the reaction detecting means. This is because in a state in which each reaction container is contained in each holding hole formed in the reaction block, the reaction liquid contained in the reaction container needs to be analyzed.
However, in this case, since it is necessary to dispose the light source and the reaction detecting means above the reaction block, there is a problem that the device enlarges. To solve the problem, it is preferable to shorten an optical path of the fluorescence between the reaction containers and the reaction detecting means, but if the distance is shortened, unevenness is generated in the light emitted from the light source and guided into the reaction liquid of each reaction container via the reflective plate between the reaction container positioned in the center of the reaction block and the reaction container positioned in a peripheral portion. That is, as shown in FIG. 13, unevenness is generated in a received state of the fluorescence detected in the camera 108 between the container in the center and the container in the peripheral portion. This is because the reaction container positioned in the center is irradiated with substantially parallel light, but an incidence angle upon the reaction container positioned in the periphery is not 90°, and this causes a problem that shade is generated by an inner wall of the reaction container, and a part of the incident light from the light source or the fluorescence or the reflected light from the reaction liquid is lacking.
Therefore, as compared with detection sensitivity of the reaction liquid in the reaction container positioned in the center, the detection sensitivity of the reaction liquid in the reaction container positioned in the periphery remarkably drops, and reliability of detection deteriorates. Therefore, there is a problem that in actual, it is not possible to detect the reaction liquid in the reaction container positioned in the periphery.
Therefore, to improve the detection sensitivity of the reaction liquid in the reaction container positioned in the periphery, it is considered that the optical path of the fluorescence between the reaction container and the reaction detecting means be lengthened, but in this case, a height dimension of a main body enlarges as described above. In this case, since the optical path lengthens, there is also a problem that the whole sensitivity deteriorates.
On the other hand, as to the reaction containers contained in the reaction block, an operation to introduce or remove the reaction container needs to be performed every time a measurement object changes. To perform such an operation to introduce or remove the reaction container, a predetermined operation space has to be formed above the reaction block. This requires means for removing the light source or the reaction detecting means from above the reaction block, means for moving the reaction block as such from below the light source or the like.
On the other hand, since the light source or the reaction detecting means is a device requiring a considerable weight, it is difficult to movably constitute the light source or the reaction detecting means. Therefore, it is necessary to move the reaction block as such from below the light source, but this reaction block itself also requires the considerable weight, and therefore special conveyance means is required. Therefore, even in a case where any optical fiber line is not used, since the special conveyance means has to be disposed, there is a problem that the cost soars owing to the increase of the number of expensive components.
Moreover, the reaction detecting device described in the above third document has a constitution in which capillary tubes each containing the reaction liquid are arranged in one row on the plane, a mirror is moved by scanning means to thereby successively guide exciting radiation to each capillary tube in a stepwise manner, and the light is converged on a convergent lens via each capillary tube to thereby send information of a reaction object to a detector. Therefore, the reaction liquid is laterally irradiated with light, and the light transmitted through the reaction liquid is converged by the convergent lens and guided to the detector in the constitution. Therefore, the only capillary tubes that can be arranged in one row on the plane can be detected once, and there is a problem that there is a restriction on the number of the tubes to be detected. Furthermore, there is a problem that all of the light source, the mirror including the scanning means, the reaction block, the respective capillary tubes, the convergent lens and the detecting means have to be constituted on the plane, and an installation area of the device itself enlarges.